Anzhelika A. Kolmakova

Efficiency of transfer of essential polyunsaturated fatty acids versus organic carbon from producers to consumers in a eutrophic reservoir

One of the central paradigms of ecology is that only about 10% of organic carbon production of one trophic level is incorporated into new biomass of organisms of the next trophic level. Many of energy-yielding compounds of carbon are designated as ‘essential’, because they cannot be synthesized de novo by consumers and must be obtained with food, while they play important structural and regulatory functions. The question arises: are the essential compounds transferred through trophic chains with the same efficiency as bulk carbon? To answer this question, we measured gross primary production of phytoplankton and secondary production of zooplankton and content of organic carbon and essential polyunsaturated fatty acids of ω-3 family with 18–22 carbon atoms (PUFA) in the biomass of phytoplankton and zooplankton in a small eutrophic reservoir during two summers. Transfer efficiency between the two trophic levels, phytoplankton (producers) and zooplankton (consumers), was calculated as ratio of the primary production versus the secondary (zooplankton) production for both carbon and PUFA. We found that the essential PUFA were transferred from the producers to the primary consumers with about twice higher efficiency than bulk carbon. In contrast, polyunsaturated fatty acids with 16 carbon atoms, which are synthesized exclusively by phytoplankton, but are not essential for animals, had significantly lower transfer efficiency than both bulk carbon, and essential PUFA. Thus, the trophic pyramid concept, which implicitly implies that all the energy-yielding compounds of carbon are transferred from one trophic level to the next with the same efficiency of about on average 10%, should be specified for different carbon compounds.

Export of aquatic productivity, including highly unsaturated fatty acids, to terrestrial ecosystems via Odonata.

Based on 31-year field study of the abundance and biomass of 18 species of odonates in the Barabinsk Forest-Steppe (Western Siberia, Russia), we quantified the contribution of odonates to the export of aquatic productivity to surrounding terrestrial landscape. Emergence varied from 0.8 to 4.9g of wet biomass per m2 of land area per year. Average export of organic carbon was estimated to be 0.30g·m-2·year-1, which is comparable with the average production of herbivorous terrestrial insects in temperate grasslands. Moreover, in contrast to terrestrial insects, emerging odonates contained high quantities of highly unsaturated fatty acids (HUFA), namely eicosapentaenoic acid (20:5n-3, EPA), and docosahexaenoic acid (22:6n-3, DHA), which are known to be essential for many terrestrial animals, especially for birds. The export of EPA+DHA by odonates was found to be 1.92-11.76mg·m-2·year-1, which is equal to an average general estimation of the export of HUFA by emerging aquatic insects. Therefore, odonates appeared to be a quantitatively and qualitatively important conduit of aquatic productivity to forest-steppe ecosystem.

Impact of weather variability on spatial and seasonal dynamics of dissolved and suspended nutrients in water column of meromictic Lake Shira

Depths of thermocline and the redox zone, concentrations of dissolved and suspended carbon, and nitrogen and phosphorus in seston were measured in the pelagial of the saline meromictic Lake Shira (southern Siberia) in different years (2007–2011); the relationship of the values for those parameters with air-temperature variations was assessed. Positive correlations between both air temperatures in the previous year and the depth of the redox zone in winter and air temperature in April and the thermocline depth in summer were revealed. In the mixolimnion, the ratio of total nitrogen to total phosphorus almost always exceeded the Redfield ratio (16: 1); seston deficiency both in nitrogen and phosphorus was monitored in different seasons and at various depths. The amount of seston in the mixolimnion in summer almost doubled the amount of seston in winter and was directly related with the depth of the thermocline. In the monimolimnion, seston was rich in nitrogen and phosphorus. The amount of seston in the monimolimnion varied in different years and depended both on the air temperature in the previous year and the size of the zone.

The role of water bugs (Heteroptera) as a potential source of essential polyunsaturated fatty acids for terrestrial consumers in steppe and forest-steppe

194 Determination of the fluxes of matter between the aquatic and terrestrial ecosystems is important both in quantitative and qualitative terms [1]. It is known that the biomass of aquatic organisms coming from aquatic ecosystems on land is not only an additional flux of matter and energy, but also a source of essential bio chemical components of food for terrestrial animals [2]. Such essential biochemical components are long chain ω3 polyunsaturated fatty acids (PUFAs)— eicosapentaenoic (EPA, 20:5n 3) and docosa hexaenoic (DHA, 22:6n 3) acids. Although these PUFAs belong to the same structural chemical family, the functions of EPA and DHA in the body are spe cific: EPA is involved in the endohoronal synthesis, which regulates the functioning of the cardiovascular system, immunogenesis, and metabolism of inverte brates and vertebrates, whereas DHA is contained in the membranes of nerve tissue and retinal cells and thus ensures the functioning of the nervous system of evolutionary developed vertebrates [3].

Component elements of the carbon cycle in the middle and lower Yenisei River

An integrated study of the middle and lower Yenisei River was performed in the summer of 2012. It involved monitoring the key elements and ecological processes associated with the carbon cycle of the river ecosystem (the study area is more than 1800 km long). Measurements of the production and destruction processes have shown the failure of the “neutral pipe” hypothesis claiming that any river is a simple drain of carbon from terrestrial ecosystems to the ocean. The Yenisei River is not a purely heterotrophic ecosystem. It also has autotrophic areas, where the primary production of planktonic photosynthesis is higher than respiration (above the Angara River and near the Bolshaya and Malaya Heta rivers). According to the data, the respiration rate of the plankton community in the river depends mostly on the water temperature and the content of inorganic phosphorous that can restrict the amount of organic matter consumed by bacterioplankton.

Differences in the amino acid content of dominant phytoplankton species from a eutrophic reservoir.

310 It is known that strong differences in the elemental biochemical composition of animals and plants limit the interaction of two first trophic components, producers and consumers, and transfer of substance and energy in ecosystems [1]. The C : N : P stoichiometric ratio and content of essential polyunsaturated fatty acids in various phytoplankton species are the main factors in aquatic pelagic ecosystems that limit the growth of primary consumers (zooplankton) at a high biomass of producers (phytoplankton) [2]. Other biochemical components of the biomass of primary producers, such as essential amino acids, are usually not considered, because the amino acid content is practically the same in all species of plankton microalgae [3–5]. However, these considerations are mainly based on the analysis of a limited number of laboratory cultures and marine species of microalgae. Data on the amino acid content in natural populations of freshwater phytoplankton are absent.

Intraspecies variability of fatty acid content and composition of a cosmopolitan benthic invertebrate, Gammarus lacustris

ABSTRACT Aquatic invertebrates are valuable dietary sources of essential polyunsaturated fatty acids, eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), for fish. Phylogeny, diet, and various ecological factors affect the fatty acid composition of aquatic invertebrates. We focused our study on the effect of ecological factors to a cosmopolitan species inhabiting lakes that differed in salinity, temperature, and presence/absence of predators (fish). To avoid the effect of phylogeny, which strongly influences the fatty acid composition of animals, we studied several populations of one cosmopolitan benthic species, Gammarus lacustris Sars. We found that differences in fatty acid percentages of G. lacustris were mainly affected by differences in their diets. Some populations preferred dinoflagellates, cryptophytes, green algae/cyanobacteria, and bacteria; other populations selected diatoms; and still other populations consumed zooplankton or allochthonous (terrestrial) organic matter. The salinity and presence/absence of fish affected the contents of EPA and DHA in G. lacustris. Populations from saline and fishless lakes had significantly higher contents of EPA and DHA. Thus, stocking of fishless lakes dominated by G. lacustris with fish could lead to a decrease in EPA and DHA contents in the gammarids. We propose that some saline and fishless lakes could be used as a source of gammarids for aquaculture fish feeding.

Fatty acid composition and content in chironomid species at various life stages dominating in a saline Siberian lake

This paper studies the fatty acid (FA) composition and content of essential polyunsaturated fatty acids (PUFAs) in the biomass of larvae and adults of chironomids from the saline Shira Lake. Species of different genera significantly differ in their larvae FA composition and essential PUFA content, and they also occupy different ecological niches: Chironomus species with a low PUFA content (0.2–0.3 mg g–1 of wet weight) inhabit a deepwater zone of the lake, while Glyptotendipes barbipes species that were richer in PUFA (2.3 mg g–1 of wet weight) dwell in the littoral of the lake. The biochemical differences are likely related to different feeding spectra of these taxa and can also be explained by the phylogenetic factor. A comparison does not find differences in the PUFA content in larvae and adults in the samples of the same species G. barbipes; i.e., we do not confirm the data on an increase in the content of these acids during the metamorphosis of chironomids. Thus, the data on the PUFA content in larvae can be used in calculations of PUFA fluxes through chironomid emergence from water bodies; however, the taxonomic affiliation of the emerged chironomids should be taken into consideration due to the high variability in the PUFA content in Chironomidae species.

Germination of Cyanobacterial Akinetes from Bottom Deposits in Water from Blooming and Nonblooming Ponds under Experimental Conditions

For several decades, the mechanisms of cyanobacterial (blue-green algal) bloom of continental inland waters has been one of the most urgent problems of freshwater hydrobiology. The following factors are generally believed to facilitate domination of cyanobacteria in phytoplankton [1, 2]: (1) a high biogenic load on water against the background of a low (<29 : 1) ratio between the concentrations of mineral nitrogen and phosphorus; (2) stable vertical stratification of the water column; (3) absence of large algophagous daphnias; and (4) favorable chemical composition of water (i.e., optimal concentrations of organic matter and metals). The role of the composition of organic substances and metals (microelements) is presently the least understood aspect of water bloom. However, the presence of one of these factors or even a combination of several factors does not provide sufficient grounds for guaranteed prediction of bloom (or absence of bloom) of a given body of water. Two small ponds located at the Krasnoyarsk outskirts (Pond Lesnoi and Pond Bugach) were studied in this work. The concentrations of inorganic phosphorus and nitrogen in these ponds were sufficiently high, whereas the ratio between the concentrations of mineral nitrogen and phosphorus was sufficiently low.